This invention relates in general to construction machinery or earth moving equipment and, in particular, to crawler type tractors.
More specifically, but without restriction to the particular use which is shown and described, this invention relates to a track roller suspension system for use with crawler tractors wherein a pair of endless track support and propel the vehicle over a supporting surface.
Crawler type vehicles such as crawler tractors are used in many applications for earth moving and construction purposes. Such crawler tractors may be generally equipped with auxiliary equipment such as a dozer blade or loader bucket for moving or loading materials, or a ripper mechanism which is utilized to break up or loosen the ground over which the crawler tractor moves.
As is known to those skilled in the art, a problem frequently encountered when using a crawler tractor for such operations results from the forces encountered on the tractor due to operation of the auxiliary equipment. These operational forces are frequently sufficient to reduce the effective contact area between the crawler track and the ground, sometimes referred to as the "track print." The reduction in size of the track print reduces the tractive force between the track and the ground thereby resulting in a less efficient use of the machine's power.
In prior art crawler tractors, the vehicle is supported on the endless tracks by a series of track rollers rotatably secured on a support structure which is fixed to a track roller supporting bogie secured to the tractor chassis. When the tractor is not operating the auxiliary equipment, a predetermined portion of the endless track is in ground contact supporting the vehicle for movement and defining a normal track print. However, when the auxiliary equipment is being utilized, for example either a front loading bucket or a rear mounted ripper mechanism, the operational capability of such equipment can greatly reduce the efficiency of the vehicle operation. Such loss of efficiency occurs because the forces applied through the auxiliary equipment cause the ground-engaging portion of the track, or track print, to be reduced.
For example, when a front end loader is utilized, the loading forces applied in attempting to load material into the bucket or raise the loaded bucket creates a downwardly directed force at the front end of the crawler tractor which will tend to raise the rear end of the crawler tractor reducing the track print or amount of track in contact with the ground. As a result, the driving force which may be applied through the track of the crawler during the loading operation is reduced, decreasing machine efficiency. Similarly, when a ripper apparatus is utilized on the crawler tractor, the force applied by the ripper unit at the rear of the tractor imposes an upwardly directed moment on the front end of the crawler which reduces the track print thereby decreasing the amount of driving force the crawler may apply during the ripping operation.
In the present invention, the vehicle supporting track rollers are rotatably secured on a resiliently suspended support structure. The resilient support of the structure permits the crawler tractor to operate with a minimum track print when auxiliary equipment is not being utilized, thereby increasing maneuverability during steer-by-driving operations. However, when auxiliary equipment, such as dozer blades, loading buckets, rippers or scarifiers, are being used the forces applied to the crawler during such operations act on the resilient suspension system to increase the track print in order to provide additional tractive force during such operations. The track print area is increased for that portion of the track nearest the auxiliary equipment thereby making additional tractive force available and increasing the stability of the machine during these operations.